Depending on your timing, could you actually check it BEFORE you get on the Ryanair flight to DUB?
I've never even thought of trying something like that...I could see timing being tight, but is there an actual rule it would violate?
You're using your coupons in the intended order - you're flying all segments...

"Yes, I haven't taken the 1st leg yet - I'm on my way there for a meeting now."

??